1. Field of the Invention
The present invention generally relates to the field of household appliances. More specifically, the present invention relates to the field of doors for household appliances. Even more specifically, the present invention relates to a porthole window for a front-loading drum-type laundry washing and/or drying appliance, such as a laundry washer or washer/dryer, a dry-cleaning laundry washer, a laundry dryer.
2. Overview of the Related Art
A generic front-loading laundry washing and/or drying appliance, such as a laundry washer or a dry-cleaning laundry washer, designed to wash laundry (for example, clothing, towels and sheets) by using water as primary cleaning solution or by using other cleaning solutions, respectively, or a laundry dryer, typically has a housing casing and an access door on the front side of the housing casing for inserting the laundry within a rotating drum inside the appliance. In the following, for the sake of exposition brevity, general reference will be made to a washing/drying machine (i.e., a washing and/or drying machine), but it is not to be understood in a limitative way.
In conventional washing/drying machines, the door, typically having a circular shape, has a circular porthole window and at least two circular frame elements fitting the porthole window therebetween. For aesthetical and practical reasons, the frame elements may be made of the same material as the housing casing, typically of lightweight materials (such as plastics or aluminium or a combination thereof), while the porthole window is usually made of high heat endurance transparent material (for example, glass), so as to allow a user to see the interior of the washing/drying machine during the operation thereof (for checking that the right washing/drying cycle is taking place regularly), without that such transparent material melts because of the relatively high temperatures to which the washing/drying machine is subject during its operation.
When the door is opened, the laundry to be washed can be loaded directly into the rotating drum and the washed/dried laundry can be removed therefrom. It is customary, for front-loading drum-type washing/drying machines, to use glass porthole windows that are of a bowl-like shape, extending inwards in the direction of the rotating drum when the door is in the closed configuration, so that in such configuration the glass porthole window fills the region between the housing casing and the rotating drum containing the laundry; in this way, a dead space between the outer casing of the washing/drying machine and the rotating drum is avoided, but at the cost of a more complex shape for the glass porthole window, and of a significantly increase in glass volume request for implementing the specific shape.
Such implementation for the washing/drying machines door exhibits critical aspects that may impair endurance and reliability characteristics thereof. In general, because of the increase in glass volume needed for making the glass porthole window, the washing/drying machine door exhibits an excessive weight with respect to the weight of most of the other components forming it (for example, the frames and a door hinge); this implies that the washing/drying machine door may be damaged relatively fast. In particular, a risk exists that the glass porthole window, because of its own weight, slightly slides from the aligned position between the frames elements towards an unwanted mismatched position.
Such mismatched position of the glass porthole window may cause substantially two kinds of drawbacks; firstly, in such condition the glass porthole window is no more able to cover precisely the dead space between the outer casing of the washing/drying machine and the rotating drum, thereby allowing water and/or detergent leakages or laundry snagging therein during the operation of the washing/drying machine.
Moreover, such mismatched position typically causes a weight re-distribution of the washing/drying machine door, thereby involving corresponding dangerous re-distributions of the force components acting on the hinge of the door, which may finally cause a break thereof.
In the state of the art, solutions are known for improving endurance and reliability characteristics of the washing/drying machines doors. For example, the document DE 195 15 040 discloses a door having a porthole window for front-loading washing machines.
The solution disclosed in such document substantially consists of an assembly consisting of a rear fixing means, glass porthole, glass porthole cover, outer frame. In particular, the glass porthole and the glass porthole cover are pressed between the outer frame and the fixing means, and are spaced apart by an elastic nose portion that is compressed under the exerted pressure. A maximum compression of the nose portion defines a distance at which the glass porthole and the glass porthole cover should be kept, in principle.
Such assembly firstly exhibits an intrinsic limitation that makes such solution not suitable in most of modern washing machines or other household or industrial appliances. In fact, the need of using the glass porthole cover (intended to prevent a user from coming into direct contact with the glass porthole, which may reach relatively high temperatures during the operation of the washing machine) as a further fixing element (in this case, a front fixing element), in addition to the provision of the rear fixing element and the frames, implies making the door assembly of the washing machine heavier, which in turn may causes hinge subsidence even in a relatively short period of use thereof.
Moreover, as it can be understood, the door shown and described in such document may suffer of the same above-mentioned drawback of misalignments of the glass porthole; in particular, although such solution provides a certain degree of stability, it results in an unsatisfactory operation condition of the washing machine. In particular, while in an off condition of the washing machine, i.e., no washing cycle is taking place for laundry cleaning, the assembly is quite effective, when the washing machine is operating the coupling is greatly reduced, thereby involving possible sliding and misalignments between the porthole window and the frames, and hence a break of the door in the same way as the known solutions, including the solution of the cited document. In fact, because of the inevitable vibrations occurring during operation of the washing machine (due, for example, to the high-speed rotary motion of the rotating drum, the water injection for cleaning the laundry or the discharging of the water-detergent mixture deriving from the rinse of the laundry), the compressed nose portion is subject to possible transversal compressions and decompressions that can make the door assembly quite less effective, thereby letting up on the nose portion and therefore causing longitudinal sliding or glass cracks of the glass porthole. For such reason, the solution disclosed in the cited document does not allow obtaining high performance doors for washing machine.